From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Performance characteristics of a low-resistance electrical circuit, focusing on current, voltage, and component wear.
| Identifier | ExFiles\Box 149\3\ scan0034 | |
| Date | 24th February 1939 | |
| -2- Here it will be seen how the current rises almost instantaneously to 2.2 amps. and falls almost as abruptly and then follows the same curve as when this low resistance is not fitted. The circuit of this arrangement is shown on sheet II. The cause of this rapid rise and fall is due to the current flowing in the low resistance circuit for the instant that both the main and auxiliary points are in contact at the same time. This circuit is non inductive so that when it breaks there is no build up of voltage and no burning or arcing. It is also clearly evident how the additional point makes contact again before the main points break causing a slight current rise and this additional low resistance circuit remains in parallel with the coil until the main points make for the next stroke. The result of this is shown by comparing the two voltage curves. When the resistance is fitted the potential between the points never exceeds 12 volts even when they separate where as without it the voltage rises to 110 volts at the break. To date we have completed 1400 hours with this arrangement and the points wear is excellent. Unfortunately it was only possible to run the pumps on air and throttle the delivery to a speed of somewhere between 10 and 20 stroke a second to fit in with the time base available. In practice when pumping petrol the time taken on the power stroke will be longer which will allow the current build up to a higher value which will also create a bigger induced voltage at the break. Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems} | ||